PT109563B - METHOD FOR IMPROVING THE DEVELOPMENT AND VALIDATION OF ANALYTICAL AND SAMPLE PREPARATION METHODS FOR ACCURATE AND REPRODUCTIVE MEASUREMENT OF PARTICLE SIZE - Google Patents

Abstract

THE PRESENT INVENTION RELATED TO A METHOD AND APPARATUS TO IMPROVE THE PRECISION AND REPRODUCIBILITY OF PARTICLE SIZE ANALYSIS BY LASER DIFFRACTION. TYPICALLY, THE PREPARATION OF DUST PARTICLES INTENDED FOR LASER DIFFRACTION ANALYSIS RECALLS THE USE OF ULTRASONIC BATHS, WHICH DISPERSE THE AGGLOMERATES OF THESE PARTICLES, THEN ALLOWING A STRICT MEASUREMENT. HOWEVER, THE ACCURACY AND REPRODUCIBILITY OF DISPERSION OF AGGLOMERATES IS AFFECTED BY WEAR, CORROSION AND AGE OF THE ULTRASOUND PROBE USED TO MEASURE MEASURES. THE DIFFERENCES IN THE PERFORMANCE OF SONICATION CAN BE COMPENSED BY VOLTAGE ADJUSTMENTS OF THE ULTRASOUND PROBE, LEADING TO A SUBSTANTIAL IMPROVEMENT IN THE PRECISION AND REPRODUCIBILITY OF THE DETERMINATION OF PARTICULAR DIMENSION.

Description

DESCRIPTION

Method to improve the development and validation of analytical and sample preparation methods for accurate and reproducible measurement of particle size

REFERENCE TO RELATED PATENT APPLICATIONS:

The present patent application benefits and claims the priority of Portuguese provisional patent application No. 109563, filed on August 2, 2016.

FIELD OF THE INVENTION

The present invention relates to a method and apparatus for improving sample preparation for measuring particle size by laser diffraction, particularly for the calibration of ultrasound probes used in the ultrasonic preparation of high cohesion powder samples for measurement particle size.

BACKGROUND OF THE INVENTION

Laser diffraction is a good technique. known for measuring particle sizes in powders, in a dry state or in liquid suspensions. A laser light is directed through the powder or suspension containing the particles to be measured. These cause light diffraction, the degree or angle of diffraction depending on the size of the suspended particles. By measuring the laser diffraction, it is thus possible to calculate the particle size of a given sample. This technique is described, for example, in the article Particle Size analysis by laser diffraction: ISO 1332, Standard Qperating Procederes, and Mie theory by Rod Jones, published in the American Laboratory, Jan. 2003, pp. 44-47.

Precisa Accurate measurement and part 5. c ul as, the average size of d istri sion of size is important especially in the pharmaceutical industry, where size quality is critical in determining how

Cltribute of the active drugs can be formulated, how stable are the active drugs and how much is their bioavailability. For certain applications, it is necessary for the particles of a drug to be formulated so as to have a variable mean particle size, at most, of ± 0.2. micron or even ± 0.1 micron. It is, therefore, an exceptional level of rigor. In the pharmaceutical industry, the precision and reproducibility of particle size measurements are essential for the development of the production and validation process, as well as for quality control and development of generic products.

Thus, there is a need to produce these particles with a high level of precision. However, this is only ensured if the analytical method is sufficiently rigorous, to the extent that it is possible to measure the particle size with the appropriate level of precision.

Unfortunately, since the laser diffraction method became a widely used technique, unexplained variations in the accuracy of particle size measurement have been reported. this technique. These inexplicable variations in the accuracy of the measurements constitute an obstacle to obtaining the aforementioned advantages and, more importantly, they prevent chemical analysis laboratories from carrying out, independently, the verification and comparison of the results obtained, by another entity. Several theories have already been enunciated to explain these variations, such as the algorithm artifacts occurring in the interpretation of laser beam diffraction, the chaotic nature of the movement of the particles, the presence of bubble peaks, thermal artifacts, dispersion artifacts dry, of artifacts of 5 optical models or the angle of incidence of the laser beam on the surface of the particles. These problems are abundantly described in the literature íl, 2, 3, 4 and 5j, having been pointed out -solutions · for the same. However, none of the proposed solutions solved the problem of the accuracy of the particle size measurement 10.

The research underlying the present invention is aimed at improving the breakdown of the tested particles.

It is widely recognized that the particles are prone to agglomerate or unite. This is particularly true in the case of particles that have been subjected to size reduction processes, such as milling, jet mill micronization or wet polishing. The particles subjected to these size reduction processes have a very high level of cohesion, i.e. the particles come together and form particle agglomerates. For this reason, it is preferable to suspend the particles in a suitable suspension medium, which will promote the breakdown of the clusters thus formed. In the absence of this suspension step, particle size measurement performed on laser diffraction equipment can result in greatly inaccurate measurement readings due to the fact that the laser diffraction method is unable to distinguish between individual, large particles, and smaller particles that came together and form a large cluster of the same dimensions.

To perform the breakdown of particles in suspension, and to increase the accuracy of particle size measurement, it is recognized the practice of placing the suspension in an ultrasonic bath, in a phase prior to the measurement of particle size. The ultrasound bath contains an ultrasound probe, which excites the particles in the suspension, causing them to break up and thus causing them to separate from each other. This process is disclosed, for example, in EP 1 879 688 BI (Orion) or WO 2008/016691 A2 (Covarls, Inc.).

During the disaggregation process, it is important that the ultrasound probe is defined with the correct voltage parameters. If the voltage parameter set is too low, the particles will not separate completely from one another or the process will take too long. In case the defined voltage is too high, the agitation of the particles can cause the individual particles to rupture to a smaller size than that resulting from the production process. It was found that in all these cases, the poor breakdown of the particles leads to an incorrect measurement of their size.

In current practice, powders of interest for particle size measurements should be subjected to one. sample preparation step to ensure that this measurement is more likely to be accurate, whenever these particles are suspended in liquid medium ·, rather than in the dry state. When in a liquid suspension, the particleboard must be fully dispersed, so that the laser beam is diffracted by individualized particles and not by particleboard. It should be noted that diffraction of the laser beam by the particle agglomerates will obviously result in incorrect measurements.

For this purpose, samples of selected powders are usually placed in an ant. i.-suitable solvent, in which they can be suspended. A dispersant may also be added to promote the breakdown of these powders. The suspension is then placed in an ultrasound bath, which comprises an ultrasound probe connected to a power source and a voltage controller. The sample is then sonicated for an established period, thus obtaining the dispersion of the agglomerates.

In commercially available diffraction equipment, such as models produced by Malvern Instruments (Malvern, UK), the ultrasound bath is provided inside the device itself, but the sample can also be prepared in an independent ultrasound bath, but adjacent to said apparatus. In this type of equipment, the voltage that is applied to the sample is provided by the analog representation on a power scale, which varies from 0% to 100% of maximum power in the manufacturer's equipment program. The user slides the power control command on the computer monitor to vary the voltage of the ultrasound probe. In equipment where the ultrasound bath is not an integral part: in laser diffraction equipment, the power can be defined in several ways; in some models, the ultrasound bath operates at a constant voltage, the duration of the sonication being the only variable that determines the achievement of different sonication levels. In other equipment, the applied energy can vary by using the percentage control of a given power, or by setting a power level in watts or volts. In other words, the methods of: definition of the energy parameters to be applied by the ultrasound probe vary according to the equipment used.

As soon as the sample is sonicated, according to. a given validated method is then introduced into the laser diffraction equipment and the measurement is performed, obtaining information about particle size, particle size distribution, surface area, etc. 10

In order to obtain an accurate measurement of the particle size of a given powder, it is necessary to perform two distinct steps: first, the analytical method must be developed and validated, each analytical method being specific to a given product. This method development is important, as it allows, in theory, the measurement to be repeated by different users even using different laser diffraction equipment, in different laboratories, and to obtain valid results - in principle the same results should be obtained when testing products from the same batch.

Currently, in the development of the method, the sonication step and its correct processing are important. In order to obtain a correct definition for analyzing the particle size of a given compound, it is necessary to perform a calibration procedure in order to obtain the correct definition of the ultrasound probe power and to determine the right sonication time for the suspension. It should be stressed that this calibration varies from product to product, since the products differ in terms of cohesion and in the way they respond to sonication, Ά power set for the ultrasound probe head is established through a controller command, the which has a scale from 0% to 100%, with 100% being the maximum power level. The power control command is therefore defined so that the user selects the power level based on a percentage of the maximum rated power for the ultrasound probe. For the -development of the validation method and procedure, a power defined by the controller is selected, being a sample suspension, containing particles of known size, exposed to sonication or ultrasound agitation. Measurement of particle size by laser diffraction is performed and recorded at regular time intervals until the complete breakdown of the particles has been confirmed, the maximum time is reached or the rupture of the particles is detected (the measurement of the particle size is smaller than the particle size of the sample, if its dimensions are known).

The process is then completed at different power levels defined for the ultrasound probe and the results are analyzed by laser diffraction, to determine the optimal power level and exposure time for the particle type of the sample ,. The power settings are then recorded as the percentage setting that must be established in the power control command. This definition of potency is then established as part of the method development procedure and subsequently repeated using different batches of the same product, to obtain robust data on which to apply the definitions when working with samples of the same product in the future. . This procedure is known as method development and validation and, given the time required to complete the entire cycle, it is normally performed only when a new product is tested for the first time. The validated definitions are then applied when using the same type of ultrasound baths and depar t 1c u size measuring equipment. 1 p o r d i f r a tio n a 1 a s e r.

After conducting the method development and validating the state of the art, the second step of the operation is a mere routine analysis, in which the user consults the method development data relevant to the product of interest, defines the parameters of the ultrasound and ultrasound head for the required sonication power and for the prescribed time, thus determining the particle size using the laser diffraction apparatus.

Theoretically, the determination of particle size by laser diffraction, given a homogeneous powder, should always present the same result. However, in practice this does not happen, and significant variations are observed even when the same batch of powder is tested on different laser diffraction devices. In fact, it has been reported that, occasionally, there is a significant deviation in the results obtained by measuring in different laser diffraction devices, but of the same manufacturer model and using the same definitions found in the same batch of a product. Tests carried out using two different devices do not always produce identical results, particularly when the precision requirements are very high - as in the case of very small particles, such as those required for inhalable products. If the target particle size is 50 microns, then a variation of 13 microns is not significant. However, if the target size is 4 microns, then the same variation is extremely significant.

Similarly, it was observed that the same device can produce different results when testing different samples from the same batch of product at different times.

problem, is still constituted by the fact that this event occurs intermittently. On certain occasions, two different laser diffraction devices have different particle size measurement data for the same batch of powder. However, on other occasions, in this case at later measurement times, it should be said, months later, that the same two devices presented concordant data, these data being substantially similar for the two devices.

It will be noted how the intermittent nature of these variations in the data obtained in the measurement tests, had one. important impact on the analytical operations of the pharmaceutical industry. Laser diffraction is considered to be one. precision analytical method, which is confirmed by the wide acceptance of this technique, not only for research and development, but still with great importance in quality control. In this role, when a manufacturer supplies a product produced in accordance with certain particle specifications and the buyer needs to verify that the said product does in fact meet the appropriate quality specifications, disagreements over the test data have already led to situations where the buyer had rejected batches of products that apparently did not meet the requirements of the characteristics of the particuias, with high costs for the manufacturer. This has been a known problem for over 20 years, but as mentioned earlier, no solution has been found. Sometimes, users resort to the purchase of new, expensive ultrasound probes, but there is no scientific basis to support this act. In other cases, it is the fault of the analysis technician, after having made costly investigations. In extreme cases, particle analysis using laser diffraction is replaced, on the product specification sheet, by another less rigorous method, but with greater reproducibility.

The present invention resides in the identification of the cause the problem mentioned above, i.e. the lack of reproducibility of the measurement results, due to differences and variations in sonication by ultrasound caused by worn out areas and / or. damaged heads in ultrasound probes. It was observed that, as the ultrasound probes were used, the respective vibration surfaces became eroded and eroded. Eroded and worn probes provide less energy, and therefore have less sonication capacity, while defective or damaged probes can sonicate the sample too much and cause the particles to rupture. Consequently, when defining the sonication power through the percentage establishment of the power, by the power control command, which was established during the development of the method and process. calibration, the power effectively delivered by the ultrasound head, may be different for: different ultrasound probes, as has now been observed on several occasions. That is, the power established by the use of the controller command, according to the development of the method and validation process, does not always result in the same voltage that is produced by the ultrasound head. The inventors found that this difference, related to the sonication power, explains the variations found in the measurements of particle size that have been reported over time.

The need for voltage control in the ultrasound probe is known and there are several references in the state of the art to this fact and to the control mechanisms used in adjusting the voltage. For example, US20100191120A1 claims an ultrasound system that comprises an ultrasound probe and a processor, in which a sensor is configured to detect a parameter level associated with an object in contact with that sensor. The processor, coupled to the probe, is configured to generate a signal, which is associated with an action, whenever a level of at least one of the parameters associated with that object is detected and which is within a certain range of parameters predetermined, including these the voltage. The ultrasound system is controlled according to changes in capacitance detected on the surface of the ultrasound probe. However, the objective of this system is to make the operation of the system itself simpler by the user, by reducing the number of manual commands. That is, the system provides information to the user and gives rise to changes in certain operating parameters, including those of voltage, which could eventually lead to compensation actions for loss of efficiency of the probe. It is emphasized that this document does not contain any disclosure that allows the expert to identify voltage variations during sonication, which are due to varying levels of corrosion of the ultrasound probe, as a fundamental cause of the imperfect dispersion of particle clusters and, consequently, result in the low reproducibility of particle size analysis by laser diffraction. Additionally, the necessary validation requirements in the pharmaceutical industry., Would not have allowed the automatic definition of a sonication power level different from the predetermined level in the method development and validation phase.

The difficulty in identifying the root reason for these variations lies in the fact that voltage changes produced by aged probes occur over very long periods and, therefore, the unexplained differences that are observed in the analysis data, to date, have not they were attributed to problems related to the sonication and dispersion of the particles and, even less, to the variation of the output voltage of the ultrasound probes.

SUMMARY OF THE INVENTION

The present invention proposes a method of application and electrical energy to an ultrasound probe in an ultrasound bath, which comprises measuring the actual voltage produced by an ultrasound head 15 of the ultrasound probe. This voltage is measured by a voltmeter connected to an ultrasound probe, which is read by the user, who subsequently uses the percent power controller until the displayed voltage is substantially identical to the desired voltage.

In a first application of this method, it is possible to develop a method of particle size analysis and validation by laser siculation and diffraction, in a correct and reproducible way, in order to prepare and analyze a powder of interest.

This method for developing and validating an analytical procedure includes a product of interest, such as, but not limited to, a pharmaceutical product, and its sonication at a given reading power, given by the power control command, while looking for the voltmeter connected to the ultrasound probe, and record it of the defined power and the corresponding voltage. While the product is sonicated at this first power level, parts of the sample are measured by laser diffraction, to obtain information on the adequacy of the chosen power definition, to perform the breakdown of the particles, as well as to identify the duration of sonication more appropriate .., for that power level, the sample is then subjected to a second and different power level, using the power controller command., the actual voltage, produced by the ultrasound probe, displayed on the voltmeter, 0 the user again adjusts the corresponding voltage on the voltmeter. Again, particle size measurements are made at various time intervals, using laser diffraction, the process being repeated until the particle size measurement stabilizes. The method development and validation step is completed at this point, and the user registers the final percentage power level established, as well as the corresponding voltage of the voltmeter (voltage, validated), used for the sonication of the sample and the duration of this. process.

These sonications, breakdowns and particle size measurements are operations that are performed for all power settings made, these settings being always verified by observing the value displayed on the voltmeter connected to the ultrasound probe.

In a second application of the present method, the user uses the data of power, percentage and validated voltage, obtained in the development of the method and validation phase to carry out the subsequent routine tests of measurement of particle size, for the same product for which the method was developed. While in the state of the art the user could only rely on the percentage power scale for measuring the power supplied to the ultrasound probe, to establish the sonicator settings, in the case of the present invention the user can adjust the control. power control by comparing the values displayed on the voltmeter with the voltage values previously validated. In this way, it is possible to adjust the percentage power scale until the voltage displayed on the voltmeter substantially matches the validated voltage and thus completing the sonicator settings and the adjustment process. The sample can now be sonicated according to the parameters of the method development and 10 validation, and later tested by laser diffraction.

It has been verified that, as the heads of the ultrasound probes age and become worn, the reading of the percentage power determined during the development of the method and validation, does not correspond to the voltage initially validated: for a certain percentage power, the the voltage measured in the ultrasound probe becomes smaller, requiring an increase in the percentage power scale, in order to obtain the voltage at the level of the validated voltage.

2.0 This adjustment, made in percentage power, compensates for the reduction in voltage observed in the worn-out ultrasound probe, thus allowing the probes to be used always at the validated voltage, regardless of their age and time of use. As a result, the suspended powder sample is always sprayed with the same power, thus being dispersed with the same level of efficiency.

It should also be noted that, in the case of method development and validation being carried out on an old and worn-out ultrasound probe 30, the user will have to reduce the power on the percentage power scale, so that the voltage displayed, on a new and higher efficiency, be consistent with the originally validated power.

Moreover, it is certain that -salientar laser diffraction equipment include their own components ^v power measurement hardware or voltage and, therefore, the inclusion of five additional voltmeter is not required, since the circuits of this equipment are able to measure the voltage actually produced by the ultrasound probe.

The present invention also relates to an apparatus for preparing samples, of a product for performing particle size measurement. This device comprises a power supply, a power-control controller, an electronic controller, capable of calculating the voltage from percentage power information provided by the power controller command and then converting the voltage from the power supply in calculated voltage suitable for the ultrasound path in an ultrasound bath containing the suspension of the particles of. interest, and a voltmeter connected to an ultrasound probe, which can be consulted by the user, to be able to vary the voltage until the validated voltage is reached. A comparator can also be used to automatically vary the voltage until the validated voltage is reached. A probe controller can integrate the voltmeter, the power controller and the comparator.

The present invention also relates to a method, in which the ultrasound energy is used to disperse, in a rigorous and reproducible way, agglomerates of particles of interest that are suspended in liquid medium.

It is also proposed, in the present invention, a method in which the actual voltage, which is supplied to an ultrasound probe, can be adjusted through a variable power control command and this adjustment can compensate for differences in sonication performance caused by different levels of wear and corrosion in the ultrasound probe.

It is also proposed here to use a sample preparation apparatus to prepare a particle sample of interest for measuring particle size by laser diffraction.

Another proposal concerns a method in which differences in. sonication efficiency, produced by different ultrasound probes, can be compensated e. reduced, by adjusting the power control command, to a certain level reaching a constant validated voltage reading 15 on a voltmeter connected to the ultrasound probe.

The present invention also relates to a method of sonicating a particle suspension for use in particle analysis by laser diffraction. This includes identification 20 of the ultrasound probe voltage definition and the sonication time required to break down the particles of a specific product, establishing the probe power by measuring the actual voltage supplied by the probe, adjusting the power settings of the probe. probe until the measured voltage is the same as the validated voltage, and the sonication of the suspension for the identified time.

In its use, the method of the present invention differs from those of the state of the art in that the user, whether in the development of a new method for application to a new product of interest, or in the performance of a routine analysis, can base not only on the power control command, as a unique way of defining the voltage of the ultrasound probe, but also on the information provided by the voltmeter connected to the ultrasound probe, since the reading given by the voltmeter provides a reading that is independent probe wear or corrosion. User 5 can thus use the voltmeter reading to adjust the power control command.

In the method development of the present invention, the user prepares the suspension of a given product of interest using the 10 methods known in the art. An initial percentage power value is defined in the control command, with 100% being the maximum power. As sonication begins, the user records the actual voltage that corresponds to the power defined in the power control command. A first size measurement by laser diffraction is then performed, with the user continuing to carry out the sonication and particle size measurement sequence, the results being recorded at regular intervals, until the complete disaggregation is confirmed, the maximum time is reached or 20 the breakage of the particles themselves is detected (the measured particle size is less than the particle size of the sample, if known). The process is completed at different power settings than the ultrasound probe, including checking and recording the corresponding voltage 25 displayed on the voltmeter, the results being analyzed by laser diffraction. At the conclusion of the process, the voltage of the voltmeter is recorded as .s.endo: the value to be used in preparing samples and tests to be carried out in the future. Preferably, particle size measurements, carried out at regular intervals, are obtained with a plurality of different power definitions. probe, the actual voltage being produced: by the probe, measured and recorded for each of the power settings, the particle size measurement being analyzed for all the different power settings and also the power level and the breakdown time optimal, for the type of particle under analysis, selected based on data collected from measurements of particle size performed for all power settings.

For the validation of the process, different samples of the same product are sonicated and tested using 10 03 final values of the first analysis. Given that the ultrasound probe's corrosion level is unlikely to increase during the method development process (which typically takes a day or so), the validation method always has a good chance of success, whether using methods 15 state of the art or method of the present invention. In this way, proof of the advantages of the present invention can only be demonstrated by validating the method in different ultrasound baths of the same model. In these circumstances, the ultrasound probes of the different baths 20 are expected to exhibit different levels of wear.

The present invention also proposes a method of sonicating a particle suspension, for use in particle analysis by laser diffraction, which comprises identifying the definition 25 of the voltage of the ultrasound probe and the sonication time of a given type of particles, setting the probe power by measuring the actual voltage produced by the ultrasound probe, adjusting the setting of the ultrasound probe power until the measured voltage is identical to setting 30 of the identified validated voltage and the sonication of the suspension over time The. i of n t. i f i c a d o

The methods of the present invention have the advantage that, by measuring the actual voltage produced by the ultrasound probe and using this value as a defined value for power, the performance variations due to aging, wear or damage of the ultrasound probes are exceeded, once the power setting of the controller is established, not as a function of a level. fixed percentage, as in the state of the art, but as a variable value in order to ensure that the voltage produced by the ultrasound probe is fixed and thus, the sonication performance is reproduced by the different probes. In this way, the d e s v i o s t o r e s u 11 a d o s are s i g n i f i c a 11 v a m e n t e reduced and, in addition, the life span of the ultrasound probes is extended, since the reduction of their power can be easily neutralized. Additionally, there is a cost-saving effect, since worn and corroded probes can be used for longer periods of time. In industrial environments, the method of the present invention allows to obtain similar or substantially equivalent results in tests carried out on different laser diffraction analysis devices, which comprise ultrasonic baths equipped with ultrasound probes having different usage times, presenting varying levels of corrosion or wear or installed in. different laboratories. This is a considerable improvement with. significant economic impact. In fact, the method of the present invention has been shown to produce a three to four-fold improvement in the reproducibility of particle size determination.

The actual voltage produced by the ultrasound probe can be measured in a commonly known way, by applying a voltmeter to any type of conventional ultrasound probe.

It should also be stressed that the method now disclosed is applicable to any particle analysis device in suspension by laser diffraction, in which the measurement system may be impacted by deficient sample preparation 5 and can be improved by this new system of sample dispersion used in sonication by ultrasound.

DESCRIPTION OF THE FIGURES

Fig. 1 shows a conventional laser diffraction analysis equipment (state of the art).

Fig. 2 shows a laser diffraction analysis equipment according to the present invention.

Fig. 3 refers to one. flow diagram of the method of the present invention, in a routine analysis.

Fig. 4 refers to a flow diagram of the method of the present invention in method development and validation.

Fig. 5 shows the particle size distribution of a first compound for 100% power in different equipment (state of the art).

Fig. 6 shows the particle size distribution of a first compound when the power is adjusted for the probe's ultrasound energy to remain constant.

Fig. 7 shows the particle size distribution of a second compound for a power of 20% in different equipment (state of the art).

Fig. 8 shows the particle size distribution of a second compound when the power is adjusted to the energy of the. ultrasound probe remain constant.

DETAILED DESCRIPTION OF THE INVENTION 5

The present invention will now be described with reference to the figures. It is to be understood that the embodiments and aspects of the invention described herein refer to examples only and do not in any way limit the scope of protection of the claims. The invention is defined by the claims and their equivalents. It should also be understood that the features of an aspect, or an embodiment of the invention, can be combined with a feature of a different aspect, or aspects, is / or different embodiments of the invention.

Figure 1 shows a representation of a laser diffraction analysis equipment, according to the state of the art. The control command la comprises a 20 percent power scale 1b, which is used to define a certain level, of power to be transmitted to an electronic motherboard 2, which calculates the desired voltage level from data input by the user. This calculated voltage level is: communicated to an electronic power controller 4 through 25 data channels 3 (which contains additional information about alarms and filters). The functions of the electronic motherboard 2 and the electronic power controller 4 are presented here as being located in different hardware components, but this is not mandatory. In other embodiments, the functions of the placebo 2 and the power controller 4 can be housed in a single component.

The power controller 4 is connected to a power supply 5, which is used by the electronic power controller 4 to generate the calculated voltage which is then sent to an ultrasound probe 6 in an ultrasound bath 1.2, which comprises a suspension 7 of particles 8 of a given product. Particles 8 are shown in Fig. 1 as having variable dimensions, in order to represent deficient sonication. The sonicated particles 8 are then channeled or taken to laser diffraction equipment 9, to make particle size measurements, which will appear recorded as particle size distributions in histograms 10. Histograms that have wide spaces 10 represent the variability in size measurements made on the same product sample in. different laser diffraction equipment, as well as the low precision and reproducibility of the method and apparatus of the prior art.

Figure 2 shows a representation of laser diffraction analysis equipment, according to the present invention. In this figure 2, the same reference numbers as in figure 1 are used to illustrate the same or similar elements. In the control command la the percentage power scale 1b was defined to give a higher power level than that used in the state machine. technique of Fig. 1, of form. compensating for the deficient sonication and the variability of results presented by him. The difference between the state of the art device, shown in Fig.2, and the device of the present invention resides in the presence of voltmeter 11, which is connected to the ultrasound probe 6.

In. certain equipment, the voltage measurement function can be included in the existing hardware, thus eliminating the installation of the voltmeter. It is also possible to build the probe controller, which comprises these elements, 5 necessary for the control of the probe. ultrasound 6. The probe controller 6 can include voltmeter 11, power controller 4, as well as a comparator, to compare the actual voltage (measured.) with the validated voltage and thus be able to adjust the power controller 4 , as explained below. The probe controller can be integrated with the ultrasound probe 6.

In practice, the user will check the voltage displayed on voltmeter 11 and define the percentage power scale 1b to 15 so that voltmeter 11 shows the validated voltage level that was determined during method development and validation. This adjustment can also be carried out automatically, through the use of a feed-back loop ”in a comparator. The calculation of the power level, the signal transmission 20 and the power generation are performed using elements 2, 3, 4 and 5 in the same way as described in figure 1. The voltage is then transmitted to the ultrasound probe 6, which only sonicates the product particles 8 contained in the suspension 7. The particles 8 are presented in a regular shape to represent an improved sonication. The particles 8 are then channeled or conducted to a laser diffraction device 9, for measuring the particle size, which appears recorded as particle size distribution in the histograms 10. Histograms 10 with less wide spaces represent the improvement in accuracy and reproducibility of the method and apparatus of the present invention.

Fig. 3 presents a flow diagram of the method for maintaining the correct sonication power. In step 100, a power value is applied to the ultrasound probe 6 of the ultrasound bath 12, using the power control command, la. The actual voltage produced by the ultrasound probe 6 is measured in step 110, through the use of voltmeter 11 connected to the ultrasound probe 6, In step 120, the voltage of the ultrasound probe 6 is then compared with the validated voltage. If a difference is established, then the voltage of the ultrasound probe 6 is maintained at a desired level, by reading the actual measured voltage, and by defining _: actual voltage supplied to the ultrasound probe 6, in step 130, using for this purpose, the electronic power controller 4, until the validated voltage is reached.

Fig. 4 presents a flow diagram of how the user can develop and validate an analytical method related to the ultrasound probe 6, in order to correctly and reproducibly identify the operating parameters for the particle breakdown of a product of interest. The product of interest includes, but is not limited to, a pharmaceutical product, such as a pulmonary drug.

In a first step 200, a first power value is chosen for the ultrasound probe 6., for the sonication of a first sample of the product of interest. In step 210, a first voltage value produced by the ultrasound probe 6 is measured and recorded, with the first defined voltage value. In step 220, the first product sample is sonicated, with the first defined power value, while in step 230, particle size measurements are made, at regular time intervals, to follow the progress of.

disaggregation of the first sample.

This process is repeated several times, since step 240, using another sample from the same batch and with. other power values, until a sufficient number of measurements have been made.

In step 2 50, a power level and a time suitable for the optimal breakdown of a particular type of particles is selected, based on the results of the breakdown of the samples. In step 2 60, the validated voltage measured in the probe, 6, is determined. which corresponds to the selected power level, these values being established, in step 27 0, as the values of validated voltage and selected time, in the settings for the sonication of the particle of interest.

The invention will now be more detailed with reference to two examples, which also contain explanations of the figures

EXAMPLE

The method of the present invention was tested in. five different laser diffraction devices, the Malvern 25 Mastersizer 2000 and Mastersizer 3000 devices manufactured by Malvern Instruments Ltd (Malvern, United Kingdom.). The Malvern Mastersizer 3000 device was also used in Mastersizer 2000 mode and thus six data sets were obtained. Each of the aforementioned devices has its own integrated ultrasound bath 30, with ultrasound probes with different usage times, used to sonicate samples before carrying out the analyzes of this study.

In carrying out the analyzes, the same batch of product was used, a pulmonary inhalation drug, this batch being obtained using a validated wet polishing manufacturing process, obtaining the highest particle size precision and reproducibility . In the observation by optical myoscopy it was possible to verify that these particles had similar physical characteristics and dimension.

Table 1 below contains the results obtained when using the state of the art method, with an ultrasound probe power level being defined in a conventional manner with the percentage power scale at maximum value. Table 2 contains the results obtained when using the improved method of the present invention.

pharmaceutical product was analyzed in. all the devices mentioned above, following the conventional method, in which the power value was defined on the controller 1b percentage power scale. A voltmeter was connected to the ultrasound probe 6, with the sole purpose of obtaining information about the actual voltage transmitted to the ultrasound probe 6. However, this information provided by the voltmeter was not used to adjust the percentage power scale in the control control it.

Samples of the same batch of pharmaceutical product were suspended in water, with the addition of one. appropriate dispersion in the integrated ultrasound bath of each device: four Malvern Masters.izer 2000 units, identified as CM0.6, CM09 ', CM0'5 and CM10, and one Malvern Mastèrsizer 3000 unit, identified as CM10. The samples were sonicated and analyzed for size by laser diffraction.

The analysis measured the particle size in the samples, and their distribution was calculated and expressed with D10, D50 and D90. When particles 8 are ordered ascending according to their mass, the corresponding values are representative of the particle size in microns, the diameter of the largest particle found in 10%, 50% and 90% of the particle mass, which is very characteristic of the particle size distribution, and therefore of the product quality. The data are shown in Table 1.

Table 1

Equipment Power (%) Probe energy. M D10 (pm) D50 ips) D 90 (pm) CM0 6 100 130 0.782 1,639 3.375 CMOS 1QQ 150 0.7 61 1,628 3,324 CM 02 100 155 0.8 51 1.79 3,641 CM0 5 100 152 0.814 1.703 3.308 CM10 (2000 mode) 100 151 1, 4 39 3, 02 6 5.78 3 CM10 (3000 mode) 100 151 1,079 2,631 4,953 Average 0.9543 2.0 695 4.0640 Standard deviation 0.2638 0.6038 1.0505 Relative standard deviation 27.64% 2 9, 18% 25.85%

The power was set at 100% of the maximum power, according to the original method development data. The energy level of the ultrasound probe was measured using a voltmeter, having varied from 130 to 155 V. Columns D10, D5Q and D90 indicate, the dimension data in each of the three classes of particle sizes, obtained for each of the six series of analyzes performed on the five laser diffraction apparatus. From the data processing, from D10, D50 and D9Q, the corresponding mean, standard deviation and relative standard deviation (standard deviation / mean) were obtained.

homogeneous physical characteristics. In this way, these data demonstrate that the method of analysis is imprecise, has a downside: reproducibility

2 Table 2 presents the results obtained by following the method of the present invention, in which the power is defined by measuring the actual voltage produced by the probe and adjusting it.

& CTU ί.Όβ νν'ιΓι t O Wattage gives γχ Ί · ’*> i wne ϊ Λ ··· .λ. · _ · 8 ^; 0 J. 0.782 .ί. , Ο, ί .‘χ: ... · f Ο: ....................... I— ' 7 «1 <S« 1 ·? s . ·. 3 υ 1,693 ί 3,847 ·. · 1 ^ν ί x / J 13 0 U, Ό ύ 8 , -1 0 ’« s? / ’· y. ·· .... * j. .1, V '· .. ·' 13; bi ; - η '.2 _f .''Ο 4 ..., ... -> ... ..., ο η *

CM10 '(3000 mode) 6: J .. 130 0.631 -------------------------------------------------! -------------------------------------------------- - ..- _and ...... i ... ...... x bzo 1 J,. <.í X. Average 0.7 08 1.7177 | 3.3967! Standard deviation Relative standard deviation Q, 06b8 8.91% ^{: z <} '<O ^{: Xi} í a>

The data were obtained according to the causative method and were calculated in the same way as the one described in Table 1.

greater, when using the method of the present invention, indicates that its precision is superior.

This improvement can also be seen in Figures 5 and 6, where the data in Tables 1 and 2 were presented, respectively. The vertical bars represent the particle size for each of the three classes of sizes D10, .050 and D90, representing the error bars the distance from the maximum data point to the average and the distance from the minimum data point to the average. Figure 4, which illustrates the present invention, shows an evident improvement when compared to figure 3, in particular by the smaller amplitude of the error bars.

These data indicate a notable and long-desired improvement in particle size analysis by laser diffraction, as they prove the advantages of the present invention, demonstrating improved precision and reproducibility of particle size measurements, in the same product, performed on different ultrasonic baths and diffraction devices 1st a r.

EXAMPLE 2

The tests in Example 1 were repeated in order to test a different compound, this time using four laser diffraction devices. The methods followed were the same: the conventional, state of the art, and the method of the present invention.

To perform these analyzes, one was used. same batch of an unidentified drug, having been obtained through a validated production process of particle size reduction and resulting in the reproducibility and precision of known particle size. When observed under an optical microscope, these particles have similar physical characteristics and dimensions.

Ά Table 3 below contains the results obtained when using the state of the art method, with a power level, from the ultrasound probe, being defined in a conventional manner, with the percentage power scale at maximum power. Table 4 contains the results obtained when using the improved method of the present invention.

pharmaceutical product was analyzed in all devices, by the conventional method, in which the power is defined with the same value, in the percentage power scale controller.

Samples of the same drug were suspended in a suitable anti-solvent, with the addition of a suitable dispersant, in an integrated ultrasound bath of each device: Malvern Mastersizer 2000 units, identified as CMOS, CM09, CM0'2 and CM05., Which were sonicated and analyzed by laser diffraction 20 for size.

obtained data are presented in Table .3.

Table 3

Equipment Power (%) Energy probe [V1 D10 (one) D50 (pm) D90 (pm) CM06 20 39 12,271 46,846 92,688 CM 09 20 60 9,787 37,519 75,988 CM 02 20 41.6 12,667 44, 53 90,043 CM 05 2 0 42.8 12,095 42.69 8 6, 662 Average 11.7050 42.8963 86.3453 From s v i o p a. -d r ã o 1.3008 3.9677 7.3320

Relative standard deviation 11.11% 9.25% 8.4 9%

The power was set to 20% of the maximum power, according to the original method development data. The energy level was measured using a voltmeter, ranging from 39 to 42.8 V. Columns D10, D50 and 090 indicate the dimension data obtained in each of the three different size classes, for each series of analyzes. performed on the four laser diffraction devices. Processing of data from D10, D50 and D90 resulted in an average, standard deviation and relative standard deviation (standard deviation / mean).

In this example,. Relative standard deviation ranged from 8% to 11%. These values indicate an average variability in the size determination method.

The same batch of product was analyzed again, in the same laser diffraction devices, after the sonication power level was duly adjusted, for each one, according to the method of the present invention.

Table 4 presents the results of the analyzes carried out according to the method of the invention, in which the power is defined by measuring the actual voltage produced by the probe, and adjusting this value, until the prescribed validated power value is reached.

Table 4

Equipment Power (%) Probe energy ί V J Dl 0 (pm) D 50 (one) D90 (pm)

CM 06 | 22 43 10,927 41,448 85,625 CM09 1 8 4 3 10,725 41,135 AT o o a? 00 CM 02 | 21 43 12,377 43.738 87,992 CM05 1 19 4 3 12,089 4 2.76 87,096 Mean | 11.5295 4 2.27 0 3 86, 17 93 Standard deviation 0.8249 m the C-J 1.7479 Relative standard deviation 7.15% 2.85% 2.03%

The data were obtained according to the method of the invention and processed in the same way as mentioned for Table 3

The percentage power scale was adjusted, in each of the ultrasound baths, so that the energy measured by the voltmeter would register the validity voltage value of 43 V. In defining this voltage, the percentage power scale was established at values ranging from 19 % to 22%.

In this second series of analyzes, the average particle size, for each of the three size classes, D10, D50 and D90, was equal to the average obtained by the state of the art method. However, the relative standard deviation showed a small improvement in the measurements of the size class 1) 10, from 11.11% to 7.15%, while the measurements in the class D50 showed an improvement three times greater and those of the class D90 showed , an improvement four times greater than the data in Table 3 obtained according to the conventional method.

This improvement can also be seen in figures 7 and 8, where the data in Tables 3 and 4 are respectively presented, in the same way as in the figures that illustrate the data in the previous example. Figure 6, illustrating the present invention, shows an evident improvement over figure 5, showing a smaller amplitude of the error bars.

The data in this example indicate that the same improvement in precision and leproQUί..ιη.ί.ι..ιθ. ^ Οο uç method, that .1.0.1 is preserved in r.xemp-io i, when a different drug is axiaiisadc

Table 5

Mastersizer 2000 - CM05 New probe without power adjustment 54 v 8.031 Ό 2 y g 2 6 s, 191 (%} PS difference between new probe and old probe ™ d _f 0 · · <. -12.091 d. .1 f J Íí But ters i ze r new probe, with power adjustment a Ί 2- 4 4 V 8, 8 3 7 3 2 _f 8 7 3 71.4 x y í% sDifference new probe and probe, old ................................. -7.56% .............................

When comparing the first analysis performed after sonication with an ultrasound probe of undetermined age, on the device

xepare ~ that the new probe of a .11rassons fitted and covers oe produx 1.r a voltage of 4 4 V, but only requires a 7% input petenole on the power scale, instead of the CM02 sonicator, which requires 20% power to produce the same 44 V. This observation confirms that the difference in power produced by the old probe and the new probe is real.

Table 6

Equipment Power (%) Energy of probe m MO (gmj 050: juml DOO (um) Mastersizer 2000 - CM 02 Old core probe undetermined age 2 0% 4 4 '7 b, 67 5 24,841 59, 3 « Mastersizer 2000 - CMOS New probe without power adjustment 20% 54V 6, · 17 8 22,505 52,870 {%; PS difference between new probe and old probe -7, n: - 9 _r 07% -10.95% Masiersizer 2000 - CMOS new probe, with power adjustment 7% 4 4 v 0.39 23.73 5b, 803 kiCDDifference PS between new probe and old probe. -4.27% - 4.4 7% -4.34%

Table 6 shows the data of the analyzes carried out on the second batch of the same product, following the same analysis protocol.

Comparing with the first analysis performed after sonication using an ultrasound probe of undetermined age, in CMOS, with the second analysis performed after sonication with.

a new ultrasound probe, in CMoi, it was observed that the particle size, in this second analysis, was about 7.4% to 11% lower in each of the three size classes.

When the third analysis was performed, again at CMQ5, the new ultrasound probe, but this time using a; of power, it was observed that the lower particle size, but with a smaller margin, about 4%, in each of the three size classes - closer to the oric measurement in CM02.

The data in Tables 5 and 6 indicate that the err <reproducibility of the method was reduced by adjusting the percentage power as a way to ensure a vo.1 ca. in.

, with justification. there was a ginal> na :: e d cage.

constant.

REFERENCE NUMBERS la Power control command

1b Power scale

Motherboard ”or motherboard

Data channels

Electronic Power Controller ·

Power supply

Ultrasound probe

Suspension

Particles

Laser diffraction equipment

Histograms

Voltmeter

Ultrasonic bath

BIBLIOGRAPHY

K. M.indgard, R. Morre11, P. Jackson, S. Batel and R. Buxton Measurement Good Practices G.uide No 111 - Good Practice Guide for Improving the Consistency of Particle Size Measureaent ISSN 1368-6550.

Amy Sabian - The Particle Experts, Problem i.n particle size ·:

Laser Diffraction Observations - Autumn 2011, Vol.15 / No. 04)

F. Storti and F. Balsamo - Particle size distributions by laser diffraction: sensitivity of granular matter strength to analyt-ical operating pro.ced.ures. In: Solid Earth Discussions,

April 2,010; .

Van. der Graaf - Sonocrystallization, Nucleation of ammonium sulfate and alpha-lactose monohydrate due to ultrasonic irradiation - Master of Science thesis, Delft University of Technology, Jan. 2011).

Lawrence C. Lynnworth - Industrial Application of Ultra-sound - A Rev.iew. II. Measurements, Tests, and Process Control Using Low Intensity Ultra-sound - IEEE Transactions on Sonics and Ultrasonics, Vol. SU-22, no. 2, Mar. 1975.

Claims (6)

1. A method to develop and validate an analytical method, related to an ultrasound probe (6), for correct identification and reproducibility of the operational parameters of particle breakdown (8) of a product of interest, characterized by understanding the following steps: i. apply (200) a first ultrasound probe power value (6), for sonicating a first sample of the product of interest, measure and record (210) a first voltage produced by the ultrasound probe (1b) with the first value of defined power; ii. sonicating (220) a first sample with the first defined power value, performing particle size measurements (8), at predetermined time intervals, to follow the progress of particle breakdown (8) of the first sample; iii. select (200) a second power value, from the ultrasound probe (6), which is different from the first defined power value, measure and record (210) the second voltage, produced by the ultrasound probe (6) with the second defined voltage value, sonicate a second sample of the product of interest, with the second defined power value, performing particle size measurements (8), at predetermined time intervals, to follow the particle breakdown progress (8) of the second sample; iv. select (250) a power and time level, for the type of particles (8) under analysis and for an optimal breakdown of these particles (8), depending on the 1/3 disaggregation results of the particles of the first sample and of the particles of the second sample; v. determine (260) the validated voltage measured in the ultrasound probe (6), which corresponds to the selected power level; and saw. establish (270) the validated voltage and time selected as the sonication settings of the particles of interest. A method according to claim 1, characterized by comprising: - the repetition (240) of the selection of the defined power values, for later analysis of samples of the product of interest; - perform additional particle size measurements, to monitor the progress of breakdown of these particles; and - select the power level and time for the type of particles under analysis, for an optimal breakdown of these particles, depending on the results of measurement of particle size for these defined power values. A method according to claims 1, characterized in that the product of interest is a powdered drug. 4. A method for the production of ultrasound energy to disperse agglomerates of particles suspended in a liquid medium characterized by using the parameters of validated voltage and selected time established using the method of claim 1 and further comprising the adjustment and definition of power to compensate for the wear and corrosion of an ultrasound probe (6). 2/3 A method according to claim 4, further comprising preparing a suspension of a sample of a product of interest in powder form in a liquid medium. A method according to claim 5, characterized in that it further comprises the measurement of particle size, of that suspension, by laser diffraction.